AWS S3 buckets cannot be publicly accessed for WRITE actions in order to protect your S3 data from unauthorized users. An S3 bucket that allows WRITE (UPLOAD/DELETE) access to everyone (i.e. anonymous users) can provide attackers the capability to add, delete and replace objects within the bucket, which can lead to S3 data loss or unintended charges on your AWS bill.
There are two methods to remove world access to your S3 bucket :
A. To Remove ACL access permissions for an S3 bucket which is world writable:
B. Perform the following steps to modify the policy :